kbdmap(5) documents 35 ASCII control characters. 32 C0 control characters plus SPACE and DEL is of course only 34 characters.
The 35th, entirely fictional, ASCII character is "ns"; snuck in between "rs" (character #30) and "us" (character #31). There is no such ASCII character name.
This fictional ASCII character can be found in three places:
* The kbdmap(5) manual page.
* Several keyboard layouts, including (for examples) share/vt/kbdmaps/ua.kbd, share/vt/kbdmaps/lt.kbd, and share/vt/kbdmaps/pt.kbd
* The kbdcontrol tool.
A superficial analysis suggests, from the placement at [Control]+[-_], that in most cases "us" is what was meant.